1. Field of the Invention
This invention relates to rotors for axial flow turbine apparatus, and in particular, to a rotor with blades having an integral tenon thereon and associated with split shroud segmented rings.
2. Description of the Prior Art
In general, an axial flow turbine apparatus comprises a casing member which confines and guides a motive fluid, commonly steam, through alternating arrays of rotating and stationary blades disposed therewithin to convert the high temperature, high pressure energy of the steam into rotational mechanical energy. The rotating blades, as is known to those skilled in the art, are mounted upon a rotor member and define a generally annular array of blades extending radially outward from the rotor. Each blade comprises an elongated airfoil portion secured to the rotor by a root portion integral therewith and terminating at its radially outward extremity in a blade tip.
It has been the practice in the art to group together a predetermined number of rotating blades within each annular array by the agency of a generally annular segmented shroud member. This has been accomplished in the prior art by providing at the tip of each rotating blade a radially outwardly projecting tenon. The shroud, generally an arcuate shaped member, has a circumferential array of openings disposed therein which are sized to receive the tenon from each of the predetermined number of rotating blades to be subtended by the shroud segment.
It has been the practice to radially engage the tenons at the extreme tip of each rotating blade with the openings in the shroud. Once engagement therebetween has been established, the prior art method of fabricating axial flow turbine rotors requires that the shroud be secured to the subtended blades by riveting or otherwise deforming the projecting tenons so as to axially and circumferentially overlap the associated shroud member. However, riveting or other prior art practices which secure the shroud to the tenons have the disadvantage in that such activity deleteriously effects the material strength properties of the tenons. Thus, as may be readily appreciated, the repeated hammering necessary in the prior art to secure a rivet into the tenon to circumferentially and axially link the shroud to the blade seriously effects and weakens the strength of the rotor fabricated thereby.
It is apparent that a rotor member which provides a secure arrangement for maintaining the shroud with its subtended blade group without the necessity of riveting or other deleterious attachment procedures is an advantageous and worthwhile improvement in the turbine art.